This proposal contains a program aimed at gaining a better understanding of the regulation(s) of nutrient transport in untransformed and transformed animal cells in culture. Outlined are the precise culture conditions that will be used to cause large (50- to 100-fold changes in transport activity for hexoses and amino acids in intact chick embryo and hamster cells. These conditions are to be exploited along two separate lines of investigatin: 1) purification of carriers and 2) identificatin of the regulatory mechanism(s). Methods for the preparation of membrane vesicles retaining carrier activity are described. Membrane vesicles are to be used to chracterize carrier activities in a system free of metabolic influences and as a primary step in carrier purification. A description of methods designed to selectively label carriers is based upon incorporations of radioactive tracers into membrane proteins during culture periods known to cause radical increases and decreases of carrier activities. Methods for selective extraction of membrane proteins are also outlined as is the possible development of artificial assay systems, reconstitution of transport in liposome preparations. Electrophoresis and autoradiography are to be used through purification and reconstitution studies in attempts to identify the hexose and amino acid carriers. Control of amino acid transport in whole cells focuses on transcriptional, translational and post-translational events. Regulation of hexose transport centers on investigations into the mechanism of turnover. The possibilities that modification of plasma membranes and subsequent degradation contribute to control is discussed and methods designed to test the possibility are described. Whenever possible, efforts are to be made to compare untransformed ("normal") cells with their transformed counterparts.